It is important to acquire vital signals daily to apply in health care, early detection of diseases, prevention of diseases, and the like. Particularly, a pulse wave propagation velocity is an important vital signal correlated with an arteriosclerosis level and a blood pressure. Therefore, measurement of the pulse wave propagation velocity is effective means when diagnosing a risk allowances in outbreak of an illness of lifestyle diseases and the like.
Here, an arteriosclerosis level and a blood pressure value greatly vary in a daily life of a test object. Therefore, measurement only performed in a resting state as in the related art is insufficient for determining risk of lifestyle diseases. In other words, for example, since states of a blood pressure and blood vessels of the test object greatly vary under variously changing environments such as a case of being exposed to rapid temperature variation, a state of lightly exercising such as jogging, a state under stress such as at work, or a state having a nightmare during sleep, it is necessary to measure the pulse wave propagation velocity in the corresponding state so as to obtain information of an arteriosclerosis level and a blood pressure value.
PTL 1 discloses a technology in which an arteriosclerosis level can be evaluated in various situations in a daily life of the test object by attaching a small and light pressure sensor to a wrist and an ankle so as not to hinder a normal life or an exercise of a test object applying no load to the test object, and continuously recording waveforms of arterial pressure by using a small-sized recording device from both sensors.